I still don't understand (they are not mentioned) how some CP costs work

How much costs:

1d6 + 2 armor/skill? and 2d6 armor/skill?

Of course 1d6+2 armor IS better because it gives you 3-armor at 1 roll so it should costs a more

How I give mind to mounted Machine gun without operator(he have aim to kill all minifigs that making something bad? 1d6? or 1d6-2? (But then it will be usless!) Or use 1d6-2 (for halfmind because it's machine and then add + 3skill to be better shooter)

The costs are all explained in Chapter 7 in the 2005 rules. Any creation, be it a minifig, spaceship, or just gun emplacement can be made using those rules.

A minifig has an armor of 1d6 (or 4, just to make things easier, as four is about average for 1d6). If you want to make a minifig have more armor, you wither give him actual Minifig Armor, or raise his armor through the creation process.

Skill is shown in that chapter as well. A minifig has 1d6 Skill, which is where one of the CP in a minifig's total cost comes from. If you want to give him a higher skill, just use the chart in Chapter 7 to see how much more CP you would have to add for the Skill level you want.

To make a gun emplacement automated, first make the gun itself, which would be just the weapons section, then give it a skill value. Add the CP for whatever skill level it is and you're set.

ending stats
a size 2 creature that is as tough as a troll(SL1) can move 4" in a turn has a skill of 1d6 and heavy plate armor covering the whole body for 2d6 in armor. value for the creature is 10cp.

game play notes: this is going to be a bastard of a creature to kill the armor and heavy hide of the creature is nominally resistant to up to 12 points of damage taken at a shot, and having 2HP helps a lot, in other words if the creature is being shot at by archers its going to take the combined effort of at least 5 archers an average dmg of 3 a trooper more likely more are needed as some will miss.

note: armor including shield is under the weapons table under the heading protection